1. Field of the Invention
The present invention relates to underground work chambers and, more particularly, pertains to an underground work chamber assembly and a method for constructing such an underground work chamber.
2. Description of Related Art
The art is generally cognizant of underground work chambers and of the drilling techniques utilized during exploration for oil, natural gases, and precious metals. Representative prior art in the field of underground work chambers is included below.
W. D. Waterman, U.S. Pat. No. 3,307,361, describes a method of constructing an underground structure.
S. Pepper, U.S. Pat. No. 1,049,528, discloses a well digger's cage.
D. J. McBride, U.S. Pat. No. 4,254,994, teaches an apparatus for gaining access to an underground chamber.
In the mining industry, work chambers or cavities in the ground, typically connected by tunnels or shafts, are constructed "in place" by miners who mine out the chamber. In order to get to the chamber location, either a tunnel or shaft is utilized. In the case of men advancing by way of a tunnel, if the soil is unstable, shields, shotcrete lining and/or rock anchors must be used for men and equipment to advance to the chamber location. In the case of men advancing by shaft, the shaft is typically drilled using drilling fluid in order to bring up the cuttings, stabilize the hole and to prevent the migration of gases. Thereafter, steel casing is installed in the shaft and grouted in place for the men to enter the shaft in order to mine the chamber.
In order to mine a chamber in potentially unstable ground conditions, workers may use a variety of shoring techniques to prevent collapse, including spilling. Shields may be utilized. In relatively stable ground, rock bolts will dot the chamber wall which supports the wire mesh or steel reinforcing and shotcrete lining. Additionally, potential gas hazards must be addressed with the men working in the confined environment. A ventilation shaft must be installed from the surface. Once a cavity is excavated and made safe, the work space must be prepared to receive the tooling, equipment and materials to be used for the intended task.
These techniques all suffer from a number of disadvantages: Workers must enter the tunnel or shaft in order to create the chamber. While doing this, the workers are exposed to all the hazards of mining a cavity, whether it be unstable ground conditions or the dangers of migrating or trapped gases. The mining of a chamber is a time consuming process. The extraordinary safety precautions required when subjecting men to the hazards of mining chambers, plus the limited space for men, tools, equipment, and materials makes the process difficult and time consuming. Once the chamber is secured, it must be prepared for equipment, tooling, and utilities to function as a work space for its ultimate utilization. This process is performed with men within the chamber in a less than ideal work space.